I recently noticed a high pitch noise coming from the bulb in my bearded dragons vivarium.
i have tried various bulbs and they all seem to follow the same pattern ..no noise when fully powered but a high pitch noise that gets worse the dimmer the bulb goes. It's probably worth mentioning that it's not audible outside the tank.
My only concern is the noise could be stressing out my bearded dragon (even though he shows no signs of stress)
i have a micro climate B1 dimmer with a 100w "reptile systems" bulb and a ceramic holder.
I don't think the noise bothers them, but I do know the humming you're talking about that goes along with dimming. Some bulbs handle this better than others. I've had good luck using halogen flood lights on a dimming thermostat. It may take some trial and error to find one that works though. The trick is to find one that provides temps that are really close without dimming, then use the dimming to fine tune the output automatically so they don't have the power cut by a whole lot at a given time.